The requirements of extended capacity and increased reliability in data communication environments has created a need for carrier-class (or carrier grade) availability. Enterprises such as mobile wireless carriers, data access providers, and fixed wireless carriers, as well as enterprises and government institutions that operate broadband wireless networks often use carrier-class infrastructure for handling their IP communications and mission critical applications. For example, to carry voice and real-time traffic in converged environments, a carrier-class infrastructure may be configured to deliver the same level of availability as the public switched telephone network.
For increased bandwidth, load balancing and availability of communication channels between nodes (e.g., switches and stations), networks often use link aggregation techniques to combine multiple physical links into a single logical link (sometimes referred to as a “link aggregation group” or “LAG”). Link aggregation techniques are designed to achieve increased bandwidth and provide redundancy to support individual physical link failures.
IEEE 802.1AX describes the most common link aggregation technique. IEEE 802.1AX was designed to increase data rates across a link aggregation group in fixed unit multiples (trunked Fast Ethernet and Gigabit Ethernet). A hashing algorithm, which may be proprietary and vary among vendors, controls distribution of traffic among the physical links of the link aggregation group. When one link fails, the hashing algorithm redistributes the traffic across the remaining physical links. When a failed link recovers, the hashing algorithm redistributes the traffic to include the recovered link.
FIG. 1 illustrates an example network 100 of four parallel gigabit Ethernet links 104a-104d (each generally referred to as a link 104) combined to create a logical link 106 supporting four gigabits per second. As shown, the network 100 includes a switch/router A coupled via the logical link 106 to a switch/router B. Switch/router A includes an aggregation engine 108, which is capable of using link aggregation to transmit and receive traffic across the physical links 104 of the logical link 106. Switch/router B includes an aggregation engine 110, which is also capable of using link aggregation to transmit and receive traffic across the physical links 104 of the logical link 106.
Traditional hashing algorithms may use information from the packet headers at different network layers to distribute traffic. At layer 2, the traditional hashing algorithms determine which outgoing port to use by hashing destination and source MAC addresses. At layer 3, traditional hashing algorithms determine which outgoing port to use by hashing fields of the IP header, most commonly the source and destination IP address. Because these methods depend on the traffic flow characteristic and patterns of the payload, traditional hashing algorithms using layer 2 or layer 3 have proven less than effective. For example, in point-to-point systems, which have only one source and one destination MAC address, traditional hashing algorithms will not have MAC address diversity to distribute the traffic over multiple physical links, because the hashing of the source and destination MAC addresses will always result in the same outgoing port. Therefore, the traditional hashing algorithms will funnel all traffic over only one physical link 104. A layer 3 hashing algorithm will produce better results, due to a larger diversity of IP addresses in the payload. However, the layer 3 hashing algorithm will not achieve effective load balancing.
Further, in wireless (e.g., microwave) communication, IEEE 802.1AX does not effectively support link aggregation. IEEE 802.1AX demands that each link provide identical capacity. IEEE 802.1AX fails to accommodate the inherently inconsistent radio link capacities of wireless links. Further, IEEE 802.1AX demands that each physical link provide unchanging capacity. IEEE 802.1AX fails to accommodate the inherently dynamic radio bandwidth changes of wireless links. Accordingly, IEEE 802.1AX does not efficiently support wireless link aggregation.
Aviat Networks solved some of these problems with a layer one link aggregation (L1LA) technique, as described in U.S. Pat. No. 8,264,953, which is hereby incorporated by reference. As described, wireless links may be aggregated. Using layer one link aggregation, Aviat Networks developed a technique of layer one rapid channel failure detection and recovery and improved capacity over wireless links.